Physics
Scientific paper
Sep 1987
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1987jgr....92.e314j&link_type=abstract
Journal of Geophysical Research, Volume 92, Issue B4, p. E314-E330
Physics
Scientific paper
Clasts of an unusual type of lunar highlands igneous rock, alkali gabbronorite, have been found in Apollo 16 breccia 67975. The alkali gabbronorites form two distinct subgroups, magnesian and ferroan. Modes and bulk compositions are highly varied. The magnesian alkali gabbronorites are composed of bytownitic plagioclase (Or2-5An82-89), hypersthene (Wo3-5En49-62), augite (Wo39-42En36-44), a silica mineral, and trace Ba-rich K-feldspar. The ferroan alkali gabbronorites are composed of ternary plagioclase (Or11-22An65-74), pigeonite (Wo6-9En35-47), augite (Wo38-40En29-35), Ba-rich K-feldspar, and a silica mineral. Trace minerals in both subgroups are apatite, REE-rich whitlockite, and zircon. The magnesian and ferroan alkali gabbronorites appear to have formed by progressive differentiation of the same, or closely related, parent magmas; the compositional data indicate that these magmas were REE-rich. The ternary plagioclase is probably a high-temperature metastable phase formed during crystallization. In composition and mineralogy, the 67975 alkali gabbronorites show many similarities to Appllo 12 and 14 alkali norites, alkali gabbronorites, and alkali anorthosites, and all these rocks together constitute a distinctive alkali suite. In addition, the alkali gabbronorites, show some similarities to KREEP basalts, Mg-norites, and some felsites. These data suggest genetic links between some or all of these types of pristine rocks. Two types of relationships are possible. The first is that alkali-suite rocks crystallized in plutons of KREEP basalt magma, and KREEP basalts are their extrusive equivalents. The second is that the alkali-suite rocks and some felsites all crystallized in plutons of Mg-norite parent magmas, and KREEP basalt magmas formed by remelting of these plutons. Additional studies are needed to resolve which of these hypotheses is correct.
Flohr Marta K.
James Odette B.
Lindstrom Marilyn M.
No associations
LandOfFree
Petrology and geochemistry of alkali gabbronorites from lunar breccia 67975 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Petrology and geochemistry of alkali gabbronorites from lunar breccia 67975, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Petrology and geochemistry of alkali gabbronorites from lunar breccia 67975 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1676056